I want to tell the girl whether to call or send a message when I am not at home.

If you feel confident of success, and you don't think girls will be surprised by your sudden confession, and your eloquence is fine, you can choose to confess by phone.

If you feel that the opportunity is fifty-fifty, and you are not good at words, you still use information to express your confession, because you can carefully prepare a confession statement, and it will not be too embarrassing if you are rejected;